1999 Isuzu Rodeo Question Water pump and Timing belt replace

I have a 99 Rodeo v6 4x4 with around 99, xxx miles on the motor and is an automatic.I'm in need of help because i'm stumped and hopefully somebody out there can help me out and others that have the same symptons.
symtoms:
(keeping in mind my vehicle ran like a champ before all this.)
1. My water pump seal was leaking so I replaced it w/a new H20 pump and seal. To do this I had to take the timing belt off too, and so I decided to replace the belt w/a new timing belt.
2. The H2O leak stopped and while putting on the belt, I thought that if the belt wasn't broken I could just put on the new belt and the timing of the engine would not be changed (still in time)and the engine will run fine. Keeping in mind the belt did not break on me while driving.
3. Put back everything and manually cranked the engine 2 revolutions to make sure there's no resistance between the lifters and cam. And there was none. Note: (I noticed a strong smell of gasoline while cranking the engine.)
4. I then started my vehicle and it hesitated for a bit, like it didn't want to start, but it did. My engine idling was okay until I went to give it some gas and then I heard backfiring through my intake air filter. I tried backing up and driving it in the drive way and it would backfire bad and stall.
5. I took everything (belt and tensiner) off and lined up the cam marks and oil pump marks to see if that was the problem and made sure that #2 piston was at tdc, because when the oil pump mark is lined up like the book says the #2 piston is a TDC and reinstalled the belt and tensiner. Manually cranked it again to line up the markings and the right(Drivers)side cam sprocket seems to be off like 1 teeth.
6. Went to start the engine again and it started up strong and fine and idle good. But it would still backfire, but less then the first attempt.
7. Repeated the timing process again and made sure that the cams where right on the markings and oil pump was on too.
8. Started it up and still the same thing. Backfire.
9. Was able to drive it with backfiring here and there, mainly when the car was within 0-30mph.
the car felt like there was no power to it.
10. Was able to get the chk engine light read and there were 3 trouble codes.
1. Egr valve--
2. Random misfires--
3.O2 sensor-(upstream)
11. I redid everything, timing marks, oil pump, changed new plugs and cleaned the egr valve and started the engine again and started fine, idles fine, and there where less backfiring when I go to give it gas. But once in a while it would backfire. And.(I can smell a strong odor of gasoline.)

I am up to this point, and very stumped. Followed the book to "how to properly replace the timing belt and markings" and still having problems. Please can anyone help me.
I haven't changed the egr valve or O2 sensors yet.
What is still wrong. HELP Please.